Compounds of general formula (I) were originally disclosed in the Hungarian Patent Specification No. P0302451 as D3/D2 receptor antagonists. In the P0302451 specification three reaction routes (A, B, C methods) are given for the preparation of compounds of formula (I). According to method “A” an amine derivative is reacted with a (tio)carbamoylchloride compound. In Example 3, Method A of P0302451 the amine is reacted with N,N-dimethyl-carbamoylchloride in anhydrous condition in the presence of triethylamine.
From the industrial point of view drawbacks of the above “A” procedure are the long reaction time (48 hours) and poor yield (65%). Besides, the end product obtained should be purified in an additional recrystallization step.
Our aim was to provide a process lacking the disadvantages of the previous process, i.e. to prepare compounds of formula (I) by an easy-to-working up manner with a shorter reaction time and better yield.